The applicant has already provided a gripping apparatus of this kind wherein rear end parts of respective gripping jaws are contained within a housing and pinions borne within the housing and pinions borne within the housing are meshed with racks formed on the above mentioned rear end parts. The gripping jaws are synchronized to operate in opposition to each other. (For example, see Japanese Utility Model application laid open No. 58044/1986.)
In the above mentioned apparatus, the racks are formed on the rear end surfaces of respective gripping pawls, and are made to form the same plane. The pinions mesh respectively, in opposition to each other, with the respective racks and mesh also with each other. Therefore there are defects in at least the three meshing parts. The backlash is large and the degree of precision in controlling the gripping operation can not be elevated. Also, there have been defectsarising from the requirement for two pinions which causes the apparatus to be uneconomical and can not be reduced in size. Further, defects occur when the respective racks are made to form the same plane as described above, in that the width dimension of the apparatus must be made larger than at least the total of the lengths of the respective racks. As a result, the contour of the apparatus becomes too wide so that even in this sense, the apparatus can not be made small.